1. Field of the Invention
This invention relates to a method capable of preventing an appearance of contour noise at which it is driven a plasma display panel in a pulse width modulation to implement a gray scale of picture and an apparatus thereof.
2. Related Art of the Invention
Recently, the plasma display panel, hereinafter PDP, attracts public attention as a display device of slim and light weight. Generally, it uses a modulation allowing the times of emitting light to be proportioned to the video signal in order to display a video signal (for example, a television signal) on the PDP. In detail, the video signal is digitized and each frame period is divided into sub-field periods corresponding to the bit number of a video data digitized. At each sub-field period, the emitting light causes by the times relative to a weighting value of each bit of the digital video data to perform the gray scale display.
Actually, in the case that a picture is displayed in 256 gray scales on the basis of a video data of 8 bits, one frame interval, in which each picture element on the PDP is displayed, is divided into 8 sub field periods SF1 to SF8. Each sub field period SF1 to SF8 is separated again into a reset period RP, an addressing period AP and a display period SP, and the display period SP has the weighting value increasing at a ratio of 1:2:4: . . . :128 according to the sub field periods. The reset period RPP and the addressing period AP come in for a share of each sub field period to be same regardless of the sub field periods. For example, the reset period RPP and the addressing period AP have the term of 1.5 ms, respectively. In such a PDP driving method, the sub field periods opposite to each bit of the video data are proceeded in a fixed sequence, for example SF1xe2x86x92SF2xe2x86x92SF3xe2x86x92SF4xe2x86x92SF5xe2x86x92SF6xe2x86x92SF7xe2x86x92SF8, as shown in FIG. 1. Due to this, a display term and a non-display term appear in one frame period such a manner of a mixed-up state according to the logical value of the pixel data, as shown in FIG. 2. In other words, the display and non-display terms existed in the frame period are arranged in a variety of patterns according the logical value of the pixel data.
As described above, since the sub field periods are proceeded in the fixed sequence, there is generated a contour noise in the picture displayed by the conventional PDP drive method. Actually, the PDP driven by the conventional PDP drive method of PWM system becomes to display the picture depending on the total quantity of the lights emitted during each sub field period. The integration characteristics of the lights is not identified with a visual characteristics accepted by the eyes of human. Due to this, the contour noise is generated in the picture on the PDP. The contour noise appears in the shape of a black stripe or a white stripe on the PDP which displays continuously two frames (or two pictures) having gray scale levels different from each other. In other words, in the case that two gray scale levels such as 127 and 128, 63 and 64,31 and 32 and so on, which allow the emitting light patterns of two frames to be entirely different from each other, are continuously displayed, the contour noise is generated. If the gray scale level of two continuous frames is changed from 128 to 127, the difference of brightness between two frames (or two pictures) is small but a time lag between the emitting patterns of two frames is enlarged to elongate the moving distance of emitting light point. In this case, there is generated the black stripe on the PDP displaying continuously the two frames because the eyes of the human does not follow the emitting point. Also, when the gray scale level of two continuous frames is changed from 128 to 127, the contour noise of the white stripe appears on the PDP displaying continuously the two frames due to the reason as described above. Such a contour noise is generated more when an object of complexion moves. In other words, the contour noise appears more in moving picture that the face or body of human moves. Further, when a color picture is displayed, it is lost a color balance by the contour noise. Furthermore, the contour noise is generated further more by the distribution of the display and non-display terms arranged in one frame period. Consequently, the quality of the picture displayed by the conventional PDP drive method is reduced largely by the contour noise. Also, the conventional PDP drive method consumes a great amount of power since a sustaining signal must be supplied continuously in the non-display term due to the distribution of the display and non-display terms.
Accordingly, it is an object of the present invention to provide a PDP drive method and apparatus which is capable of restraining a contour noise in a picture displayed on a PDP.
Another object of the present invention provides a PDP drive method and apparatus which is capable of restraining a contour noise in a picture displayed on a PDP and reducing a power consumption.
In order to achieve these and other objects of the invention, a PDP drive method according to one aspect of the present invention allows one frame to be consisted of a plurality of sub fields each having a different weighting value for a brightness so as to display a video signal of gray scale. The sub fields are differently arranged along with a distribution of logical values in the video data for one frame, thereby dividing the one frame into a display interval and a non-display interval.
In a PDP drive method according to another aspect of the present invention, the plurality of the sub fields are equal to sub fields without a sub field having a least weighting value for the brightness, respectively.
Further, a PDP drive apparatus according to still another aspect of the present invention includes: signal input means for receiving a video signal; address drive means for driving address electrodes on the plasma display panel depending on the video signal from the signal input means; a frame memory connected between the signal input means and the address drive means, the frame memory storing temporarily the video signal; sustain drive means for driving sustain electrodes on the plasma display panel; and control means for controlling the sustain drive means to allow one frame to be consisted of a plurality of sub fields each having a different weighting value for a brightness so as to display a video signal of gray scale and to divide a frame period into a display interval and a non-display interval.
Furthermore, a PDP drive apparatus according to still another aspect of the present invention includes: signal input means for receiving a video signal; address drive means for driving address electrodes on the plasma display panel depending on the video signal from the signal input means; a frame memory connected between the signal input means and the address drive means, the frame memory storing temporarily the video signal; sustain drive means for driving sustain electrodes on the plasma display panel to allow one frame to be consisted a plurality of sub fields each having a different weighting value for a brightness; and control means for controlling the sustain drive means to allow one frame to be consisted of a plurality of sub fields without a sub field having a least weighting value for the brightness.